Heat can be removed from a device (e.g., transistor, power amplifier, etc.) in an integrated circuit chip using either the substrate itself down to a heat sink, or using wiring that is formed over the device as a heat path for transferring heat away from the device and out of the top of the chip. Such wiring, however, typically has a primary purpose of carrying electric current within the chip and is not primarily optimized for heat transfer. The electric current generates its own heat within the wiring through resistive heating, and the combination of resistive heating and heat transfer from devices can degrade the reliability and the current handling capacity of the wiring.
According to Moore's law of scaling, both the current density and the circuit density increase with each generation. In combination with exotic substrates with limited thermal conductivity such as GaAs or silicon-on-insulator (SOI), the thermal budget limitations in a chip are becoming more and more severe. Circuits or subcircuits typically use the full power budget for only a limited amount of time, often for fractions of milliseconds. With current technology, the power and temperature budget need to account for the heat generated during these periods.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove, particularly of a temporal nature.